Absorption refrigeration



Jan. 1, 1952 w, G KOGEL 2,580,443

ABSORPTION REFRIGERATION Filed May 1, 1948 Patented Jan. 1, 1952 ABSORPTION REFRIGERATION Wilhelm Georg Kiigel, Stockholm, Sweden, as-

. signor to Aktiebolaget Elektrolux, Stockholm,

Sweden, a corporation of Sweden Application May 1, 1948, Serial No. 24,545

In Sweden May 7, 1947 15 Claims.

1 My invention relates to absorption refrigeration systems in which provision is made for transferring liquid absorbent to a part of the system normally free of such absorbent to modify the normal operation of the system, such as, for example, to efiect defrosting of the evaporator or cooling element.

1 It is an object of my invention to effect improvements in the manner in which liquid-absorbent is transferred from the absorption liquid circuit to a higher located place in systems of this type, particularly to provide a new arrangement for raising such liquid by vapor lift or thermosiphon action in order to obtain better pumping as well as enable liquid to be raised through a relatively great height. More particu larly, it is an object to provide .such a new arrangement for raising liquid from the absorption liquid circuit to a higher located place in the system by a vapor lift tube or-gas pump to which heat is supplied in a controlled manner at a relatively high temperature from a heating flue associated with the vapor expulsion unit of the refrigeration system. Further, it is an object to raise absorption solution relatively weak in refrigerant to a higher located'place in the system by such a vapor lift tube or gas pump having provisions for supplying heat thereto when desired from the heating flue, preferably with the aid of a controllable heat transfer member, at a sufficiently high temperature to insure positive starting of the pumping action under all operating conditions encountered.

In accordance with my invention absorption solution to be raised to a higher located place in the refrigeration system is diverted from the absorption solution circuit to a region of a vapor lift tube or gas pump which is removed from the extreme lower end thereof, the portion or section of the lifttube projecting downwardly from the region absorption solution is supplied thereto serving as a liquid pocket adapted to receive heat from the heating flue of the vapor expulsion unit. Since heat is applied to the lower end of the heating flue constituting the heat input section which is at a higher temperature than other portions of the flue removed from the heat input end, the downwardly extending liquid pocket of the vapor lift tube is advantageously arranged to receive heat from such heat input section with the aid of the controllable heat transfer member. The heat transfer member may comprise an hermetically sealed heat transfer system containing avolatile fluid, such system having a lower vaporization portion heat conductively connected to the heat input section of the heatingflue and'within which the liquid pocket of the vapor lift tube is disposed, and an upper portion with- 2 in' which the volatile fluid may be withheld from the vaporization portion or allowed to flow thereto when desired to initiate pumping of absorption solution from the absorption solution circuit to a higher located place in the system.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the claims. The invention, both as to organization and method, together with the above and other objects and advantages thereof, will be better understood by reference to the following description taken in connection with the accompanying drawing forming a part of this specification, and of which the single figure more or less diagrammatically illustrates an absorption refrigeration system embodying the invention.

In the drawing I have shown my invention in connection with an absorption refrigeration system of a uniform pressure type which is Well known in the art and in which an inert pressure equalizing gas is employed. Such a refrigeration system comprises a generator or vapor expulsion unit! 0 including a, boiler or pipe H containing a refrigerant, such as ammonia, in solution in a body of absorption liquid, such as water. Heat is supplied to the boiler II from a heating tube or flue l2 thermally connected therewith at M, as by welding, for example. The heating tube I! may beheated in any suitable manner, as by an electrical heating element disposed within the lower part of the tube [2 or by a liquid or gaseous fuel burner which is adapted to project its flame into the lower heat input end of the tube.

The heat supplied to the boiler I I and its contents expels refrigerant vapor out of solution and such vapor passes upwardly from the vapor expulsion unit I 0 through an air cooled rectifier l5 into an air cooled condenser 15 in which it is condensed and liquefied. flows from condenser l6 through conduits l1 and I8 into a cooling element or evaporator IS in which it evaporates and diffuses into an inert pressure equalizing gas, such as hydrogen, which enters through a conduit 20. Due to evaporation of refrigerant fluid into inert gas, a refrigerat ing effect is produced with consequent absorption of heat from the surroundings. V

The rich gas mixture of refrigerant vapor and inert gas formed in cooling element l9f1ows from the upper part thereof through a conduit 2|, one passage of a gas heat exchanger 22, conduit 23 and absorber vessel 24 into the lower end of an absorber coil 25. In absorber coil 25 the rich gas mixture flows counter-current to downwardly flowin absorption liquid which enters through a conduit 26. The absorption liquid absorbs refrigerant vapor from inert gas, and inert gas weak Liquid refrigerant in refrigerant flows from absorber coil 25 in a path of flow including conduit 2?, another passage of gas heat exchanger .22 and conduit into the lower part of. the cooling element I91.

The circulation ofgas in the gas circuit just described is due to the difference in specific weight of the columns of gas rich and weak, re spectively, in refrigerant vaporc Since the column of gas rich in refrigerant vapor andfiowing from cooling element I 9 to. theabsorber coil is heavier than the colum-n'of gas weakin refrigerant and flowing from the absorber coil- 25 to cooling element IS, a force is produced or de veloped within the system for causing circulation of inert gas in the manner described.

Absorption solution enriched in refrigerant flows from the absorber vessel 24 through a cond uit 28 andan inner passage or pipe 29* ofaliquid heat exchanger 30 which is disposed about the lower. part of the. vapor expulsion unit 1.. The

liquid flows from theinner pipe- 29 of the liquid heat exchanger into the boiler H at apoint-whi'ch is at a level below the liquidl'evel in. the absorber 2" and below the liquid level of the column of liquid" contained in the boiler. From the. lower ii.

closed end of the boiler Ii liquid passes into the lower end of a' l'ifttube or pump pipe 31 in ther-' mal exchange relation with. the'heating'. tube [2- at 3'2', as lay-welding, forex-a'mple.

Liquid is raised by thermosiphon or vaporliquid lift action through pipe 31' to. the: upp r part of a-standpipe or riser-.33 which. is connected at its extreme-upper end. to an upper extension of theboiler Hi and at its lower end to the outer passage or pipe 34.- of. the liquid heat exchanger 1' 30; Refrigerant vaporexpelledout'of solution in "changer 30 are usually embedded in suitable inboiler Hi, together with refrigerant entering the upper extension of thebo'iler from the standpipe or riser 3-3, flows upwardly from the vapor expulsi'on unit I ll tothe condenser: I6, as previously explained. The absorption liquid; from which refrigerant vapor has. been" expelledi flcwss from; the'standpipe. 33 through the outer passage:- 34 of the liquid. heat exchanger and conduit: 2% into the upper part of absorber coilz25 The: circulartion of absorption. solution inthe liquid circuit just described isreff'ected by raising. of liquid through pipe 3'! The principal part of generated vapor: pr

duced in: the vapor expulsion unit lfi is expelled from solution in boiler pipe H, and liquid of decreasing refrigerant concentration flows downwardly in? the boiler pipe to therbottomciosedxend thereof.

lower portion of the boiler pipe I i and the:heat+- ing tube. l2. In this way excessive expulsionof refrigerant: vaporfrom sol'utionirr the. lower part of boiler pipe H is prevented, thereby avoiding undesirable decrease in concentration of the; ab- SOIDfiOIL solution and consequent increase inv its temperature. In. order to prevent excessive heat-- ing' of the-expelled vapors passingfrom the boiler pipe- H, the upper portion thereofis desirably thermally sep-aratedfrom the heating tube I2. As shown, the boiler pipe H diverges from the heating tube l2: ata level immediately abovethe level at which absorption solution is maintained in the boiler pipe. In this manner superheating of expelled vapor is avoided and rectification in the-air cooled rectifier i5 is accomplished more effectively, so that aminimum quantity of. vaporof absorption liquid will accompany refrigerant vapor passing to the condenser l6.

Theparts of the generator or vapor expulsion.

In. certain instances itisdesirable to: provide a thermal. gap or air space 35 between the sulatin material contained within a metal shell having openings at the top:- and; bottom thereof through which the open ends of the heating tube I2 project. In order to simplify the drawing, such an insulated enclosure for the vapor expulsion unit,. which is Well known in the art, has not been shown.

The outlet end of condenser I6 is connected by an upper extension of conduit l8, vessel 38 and conduit 3'! to apart of the gas circuit, as at one end of gas heat exchanger 22, for example, so that. any inert gas which may pass through the condenser I6 can flow into the gas circuit. Refrigerant vapor not liquefied in the condenser flows through the upper part of conduit l8 to displace inert. gas in. vessel 36 and. force. such. gas through. conduit 31 into the gas. circuit; The effect. of forcing. gasinto the gas circuit in this manner: is. to raise the. total pressure in the. entire. system. whereby. an adequate condensing pressure is. obtained to. insure condensation of refrigerant vapor in condenser Hi.

In order to increase the temperature of. cooling element. l9 when. it. is desired to melt frost. which may accumulate thereon, provision is made, as? will be. explained presently,v for raising warm ab.- sorption solution from the standpipe 33 through a riser conduit 38 into a. conduit 39 from which theabsorption solution flows by gravity into cooling element |'9. In this manner rapid defrosting. is eiiecteddue to the relatively high temperature towhich thesolution is heated in the vapor expul sion-.unit l0.. The. absorption solution passes from cooling element ISthrough the gas. heat exchangen 21 to. the absorber vessel. 24.

The conduit 38. constitutes a. vapor lift tube orpump'pipe. through. which absorption solution is. raised. when desired. by heat derived from the heating. flue. ['2 with the aid of acontrollable heat transfer member. In. the embodiment of the invention. illustrated,.the heat transfer member comprises. a secondary heat transfer system including a vertically extending conduit or section 40 having the lower portion thereof in thermal-exchange relation with. the heating. tube 12 at. as by welding, and a bulb or upper portion &2. flexibly connected at 43. to the upper end of the vertical section. 40.

The heat transfer system is hermetically sealed andlis. charged withia. volatile fluid substantially" all of. which is held. in the bulb 42 when the latter is in the position shown in the drawing. When it is desired to effect defrosting of the cooling element l9, the bulb 42.is raised from the. position shown, so that fluidwillflowtherefrom by grav-. ity to-the lower. portion. of. the vertical section 40. The-lower portionof the vertical section 49 constitutes" the vaporization portion. of the heat transfer system. in whichthe fluid is vaporized by heat. taken up from the heating tube l2. The vapor formed in the bottom of the vertical section 40- is partly condensed in such vertical. section and gives up heat to the conduit 38 and its contents-to raise absorption-solution by thermosiphon or vapor lift action from standpipe 33 to the cooling element 19. Such lifting of absorps tionsolution. continues until. all of the vapor is condensed in. the bulb 42 which previously has beenreturned to-its. lower position show-n in the drawing. In this way substantially all of the volatile fluid is. held back from the lower. vaporization portion of the vertical section 40, and

heattransfer. to the conduit 38 at. asuflicientrate 44 to the standpipe 33, and the lift tube 38 in effect is extended downwardly from the region conduit 44 communicates with the standpipe 33 by a pipe section 45 which is closed at its lower end and forms a dead-end liquid pocket. The dead-end liquid pocket 45 projects downwardly from the highest point of the liquid heat exchanger 30 and is adapted to receive heat from the "heating flue II. In the preferred embodiment of the invention shown, the pipe section 45 is disposed within the lower portion of the vertical section 40 of the heat transfer system which can be rendered operable, when desired; for effectively utilizing the heating flue l2 to supply heat to the lower extended portion or pipe section 45 of the lift tube 38.

' During normal operation of the refrigeration-" system when a source of heat is applied to the.

lower heat input section of the heating flue I2,

and cooling element I9 is producing a refrigerating effect, the pipe section 45 contains absorption solution which is relatively weak in refrigerant and flows therein through the conduit from the lower end of standpipe 33. Since the lower portion of the vertical section 40 of the heat transfer system is heat conductively connected at 4| to the heating flue I2, the lower end of the vertical section 40 becomes heated and heat is radiated from the inner wall surface thereof to the pipe section 45. Such heating of the pipe section 45 by radiated heat is insuflicient to ren der the lift tube 38 operable to raise solution by vapor lift action. However, the radiated heat-is taken up by the pipe section 45 and the concentration of refrigerant in the absorption solution therein gradually becomes reduced due to such heating. When the same body of absorptionsolu tion in the pipe section or pocket 45 is held therein for a sufdciently long interval of time and not displaced or replenished by other absorption solution during periods when the pump pipe 38 is ineffective to raise solution therethrough, the

liquid in the pipe section 45 may eventually have such a low concentration of refrigerant that it consists substantially entirely of absorption liq- When it is desired to raise warm absorption solution from the standpipe 33 into the cooling element [9, the bulb 42 is raised to cause the volatile fluid therein to flow to the bottom of the vertical section 40 of the heat transfer system,

The volatile fluid is vaporized by heat supplied by theheating flue l2, and heating of the liquid in the pocket 45 will take place at a sufliciently rapid rate to bring such liquid to its boiling teniperature even when the liquid is substantially"en-' tirely absorption liquid alone. At the same time heat is supplied at a sufliciently rapid rate to the lift tube 38 and solution therein to cause expulsion of vapor and effect raising of warm absorption solution therein by thermosiphon or vapor lift action into conduit 39 from which the raised solution flows by gravity into cooling element H to effect rapid defrosting.

4 By providing the pocket 45 which extends downwardly from the highest point of the liquid heat exchanger 30 adjacent the region from which absorption solution is diverted into the pump p pe 38. and utilizing such pocket as-a downward projection of the pumppipe itself, several advantages are realized. In the ilrst'place, the pocket 45 is disposed adjacent the lower heat input end of the heating flue l2 at whichregion heat can be supplied at the highest possible temperature to the pocket and liquid held therein. Secondly, since the pocket is in alignment with the pump pipe 33 and serves as a downward extension thereof, the vapor bubbles formed therein and rising into the lower end of the pump pipe acquire substantial velocity, thereby promoting lifting of liquid in the pump pipe by vapor lift or thermosiphon action. In effect, the pipe section 45 acts to increase the actual reaction head under which solution is raised in the pump pipe 38 and creates an effective reaction head of greater height which not only produces more rapid pumping of solution but also enables the solution to be raised to a higher lever, This is particularly advantageous in an embodiment of the invention like that shown and just described in which the warm absorption solution raised to a higher level is relatively weak in refrigerant and hence requires heating at a higher temperature than absorption solution relatively rich in refrigerant to establish effective pumping of liquid by vapor lift action.

Further, by providing the downwardly extending liquid pocket 45 and locating such pocket at the same level or elevation at which heat is taken up from the heating tube [2 by the controllable heat transfer member, heat is transferred more or less directly to the pump with the aid of the pipe section or liquid pocket 45. All of the vapor bubbles formed in the liquid pocket 45 and passing upwardly therefrom are not only efiectively utilized to raise solution by vapor lift action in the pump pipe 38, but also utilized to expel refrigerant vapor from solution in the parts of the pump pipe 38 located above the region conduit 44 is connected thereto, so that the pumping action will be improved. This is so becausethe vapor bubbles of absorption liquid passing from the pocket 45 into the pump pipe 38 rise into lower temperature regions in which such vapor bubbles often collapse and condense, and the heat of condensation thus liberated is effectively utilized to cause expulsion of refrigerant vapor from absorption solution which enters the pump pipe through the conduit 44 and the refrigerant concentration of which is higher than that of the liquid in the pocket 45.

Modifications of the embodiment of my invention which I have described will occur to those skilled in the art, so that I desire my invention not to be limited to the particular arrangement set forth. Thus, a heat transfer member of'a type different from the secondary heat transfer system shown and described above may be employed to supply heat from the heat flue at will and when desired to the liquid pocket 45. There: fore, I intend in the claims to cover all those modifications which do not depart from the spirit and scope of my invention.

What is claimed is:

1. "In an absorption refrigeration system having a plurality of interconnected parts, a heating flue'having a lower heat input end, a circuitfor absorption solution comprising parts including a liquid heat exchanger, boiler element and a first vapor lift tube, said element and said first lift tube being in thermal contact with said heat-- ing flue, said heating flue and element having portions projecting downwardly from the highest point of the liquid heat exchanger, connecting means for conducting absorption solution from said. circuit to'ai higher located. partin said sys-' tem including a second vapor lift tube connected to receive absorption solution at one region anddeliver raised solution tosaid higher located part, and said second lift tube having a portion proiecting downwardly from said solution receiving region which is adapted to receive heat from. the downwardly projecting portion of said heating flue, the portion of said. second lift tube extending above said solution receiving region being arranged to receive substantially all of the vapor formed inthe downwardly projecting portion of said second lift tube and passing upwardly therefrom.

2. In an absorption refrigeration system havinga plurality of. interconnected parts, an upright heating flue having a lower heat input end, a circuit for absorption solution comprising parts ineluding a liquid heat exchanger, a boiler vessel and a first vapor lift tube, said vessel and first lift tube being in thermal contact with said heating flue, said heating flue and vessel having portions projecting downwardly from the highest point of the liquid heat exchanger, connecting means for conducting absorption solution from said circuit to a higher located part in said system including a second vapor lift tube connected to receive absorption solution at one region and deliver raised solution to said higher located part, said second lift tube having a portion which projects downwardly from said solution receiving region, and structure operable to alter the thermal connection of the downwardly projecting portion of said second lift tube and the downwardly projecting portion of said heating flue.

3. In an absorption refrigeration system having a plurality of interconnected parts, a heating flue having a lower heat input end, a circuit for absorption solutioncomprising parts including a liquid heat exchanger, a boiler pipe and a first vapor lift tube, said pipe and first lift tube being in thermal contact with said heating flue, said heating fiue and boiler pipe having portions projecting downwardly from the highest point of the liquid heat exchanger, connecting means for conducting absorption solution from said circuit to a higher located part in said system including a second vapor lift tube connected to receive absorption solution at one region and deliver raised solution to said higher located part, said second lift tube having a portion projecting downwardly from said solution receiving region, and a secondary heat transfer system constructed and arranged to supply heat when desired from the downwardly projecting portion. of said heating flue to the downwardly projecting portion of said second lift tube.

4. A system as set forthv in claim 3 including means embodied in said secondary heat. transfer system for manually initiating operation thereof. and automatically stopping operation thereof after an interval of time.

5. A system as set forth in claim 3 in which said secondary heat transfer system comprises an hermetically sealed structure containinga volatile heat transfer agent having an upper condenser portion and a lower vaporization portion, said lower portion being thermally connected to said flue and having the downwardly projecting portion of said second lift tube disposed therein an spaced therefrom.

6. In an absorption refrigeration system having a plurality of interconnected parts, a heating flue having a lower heat input end, a circuit for absorption solution comprising parts including a' boiler-vessel and a first vapor lift tube. connected to saidfiue to cause expulsion otreirigerant vapor from solution. and raise solution'to promote circulation of solution in said. circuit. connecting means for conducting absorption solution from said circuit to a higher'located part insaid system including a second vapor lift 'tube which is closed at itslower end. and connected to. receive solution from said circuit at .a-region removed from and above such closed end and. deliver raised liquid to said higherlo'catedv pm, the portion of said second lift tube between the solution receiving region and the lower closed endthereof being adapted to be heated by said heating flue.

7. In an absorption refrigeration system having a plurality of interconnected parts, an upright heating flue having a lower heat inputend,,'a circuit for absorption solution comprising: parts including a boiler element and a first vapor lift. tube thermally connected to said flue to causeexpulsion of refrigerant vapor from solution and raise solution to promote circulation of solution in said circuit, connecting means for conducting; absorption solution" from said circuit to a higher located part in said system including a. second vapor lift tube which is closed at its lower end and connected to receive solution from said circuit at a. region removed from and above such closed end and deliver raised liquid to said higher locatedpart, the portion of said second lift tube between the solution receiving region and the lower'closedend thereof being disposed adjacent the lower heat input section of said heating flue, and struc-- ture operable to alter the thermal connection. of; the last-mentioned portion of, said second lift tube and the lower heat input section of said located part in said system including a second:

vapor lift tubewhich is closed at its lower end and connected to receive solution from said circuit at a region removed from and above such closed end and deliver raised liquid to said higher located part, the portion of said second tube between the solution receiving region and the lower closed end thereof forming a dead-end liquid pocket, at

least the portion of said second lift tube forming saidpocket being adapted to receive heat from the lower heat input section of said fiue.-

9. In an absorption refrigeration system having a plurality of interconnected parts, a heating flue having a lower heat input end, a circuit for absorption solution comprising parts including a boiler element and a first vapor lift tube thermally connected to said flue to cause expulsion of refrigerant vapor from solution and raise solution to promote circulation of solution in said circuit, connecting means for conducting absorption solution from said circuit to a higher locals-- ed part in said system including a second vapor lift tube which is closed at its lower end and connected to receive solution from said circuit at a region removed from and above said closed end.

and deliver raised liquid to said higher located part, the portion of said second tube between the solution receiving region and the lower closed end thereof forming a dead-end liquid pocket, said pocket having a cross-sectional area large enough to permit free relative movement of vapor and liquid therein and the portion of said second lift tube above the solution receiving region having a cross-sectional area small enough to prevent free relative movement of vapor and liquid therein, at least the portion of said second tube forming said pocket being adapted to receive heat from said heating flue.

10. A system as set forth in claim 6 in which said second lift tube is connected to receive absorption solution weak in refrigerant.

11. A system as set forth in claim 6 in which the principal part of the refrigerant vapor expulsion is effected in said boiler vessel and said second lift tube is connected to receive absorption solution from said circuit after the solution is deprived of refrigerant in said boiler vessel.

12. In an absorption refrigeration system having a plurality of interconnected parts, a heating flue having a lower heat input end, a circuit for absorption solution comprising parts including a boiler vessel and a first vapor lift tube thermally connected to said flue to cause expulsion of refrigerant vapor from solution and raise solution to promote circulation of solution in said circuit, connecting means for conducting absorption solution from said circuit to a higher located part in said system including a second vapor lift tube which is closed at its lower end and connected to receive solution from said circuit at a. region removed from and above such closed end and deliver raised liquid to said higher located part, the portion of said second lift tube between the solution receiving region and the lower closed end thereof being disposed alongside the portion of said first lift tube thermally connected to said heating flue and also adapted to receive heat therefrom.

13. In an absorption refrigeration system having a plurality of interconnected parts including a cooling element, a heating flue having a lower heat input end, a circuit for absorption solution comprising parts including a boiler vessel and a first vapor lift tube thermally connected to said flue to cause expulsion of refrigerant vapor from solution and raise solution to promote circulation of solution in said circuit, connecting means for conducting absorption solution from said circuit to said cooling element including a second vapor lift tube for pumping solution through a greater height than that in said first lift tube, said second lift tube being closed at its lower end and connected to receive solution from said circuit at a region removed from and above such closed end and deliver raised liquid to said cooling element, the portion of said second lift tube between the solution receiving region and the lower closed end thereof being adapted to re ceive heat from said heating flue.

14. In an absorption refrigeration system having a plurality of interconnected parts including a cooling element, an upright heating flue havin a lower heat input end, a circuit for absorption solution comprising parts including a liquid heat exchanger for conducting solution in a generally vertical direction therethrough, a boiler vessel and a first vapor lift tube, said vessel and first lift tube being thermally joined to said heatin flue to cause expulsion of refrigerant'vapor from solution and raise solution by vapor lift action to promote circulation of solution in said circuit, said flue and vessel having portions projecting downwardly from the highest point of the liquid heat exchanger, connecting means for diverting absorption solution from said circuit to said cooling element including a second vapor lift tube connected to receive absorption solution at one region and deliver raised solution to said cooling element, said second lift tube having a portion which projects downwardly from said solution receiving region, and means for supplying heat from the downwardly projecting portion of said flue to the downwardly projecting portion of said second lift tube, the portion of said second lift tube extending above said solution receiving region being arranged to receive substantially all of the vapor formed in the downwardly projecting portion of said second lift tube and passing upwardly therefrom.

15. In an absorption refrigeration system of the inert gas type having a plurality of interconnected parts, an upright heating flue having a lower heat input end, a circuit for absorption solution including a liquid heat exchanger having several passages for conducting solution in a generally vertical direction therethrough and a vapor expulsion unit comprising first and second conduits and a first vapor lift tube, at least one of said conduits being thermally connected to said flue, said first conduit and flue projecting downwardly from the highest pont of said heat exchanger, said first conduit being closed at its lower end and connected to receive absorption solution from a passage of said liquid heat exchanger at a region removed from and above such closed end, said first lift tube being thermally joined to said fiue and connected to receive absorption solution from the lower part of said first conduit and deliver raised solution to the upper part of said second conduit which is in communication with another passage of said liquid heat exchanger, connecting means for conducting absorption solution from said circuit to a higher located part in said system including a second vapor lift tube connected to receive absorption solution from said second conduit at one region and deliver raised solution to said higher located part, said second lift tube having a portion which projects downwardly from said solution receiving region, and means for supplying heat from the downwardly projecting portion of said flue to the downwardly projecting portion of said second lift tube, the portion of said second lift tube extending above said solution receiving region being arranged to receive substantially all of the vapor formed in the downwardly projecting portion of said second lift tube and passing upwardly therefrom.

W'ILHELM GEORG KCGEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,357,340 Miller Sept. 5, 1944 2,402,417 Kogel et a1 June 18, 1946 FOREIGN PATENTS Number Country Date 609,619 Great Britain Oct. 5, 1948 

